
REGGIE C. answered 09/23/19
Experienced Tutor Specializing in IT Systems/Security |MSc.|Cybersec
A many-to-many relationship refers to a relationship between tables in a database when a parent row in one table contains several child rows in the second table, and vice versa. Many-to-many relationships are often tricky to represent.
The many-to-many relationship is usually a mirror of the real-life relationship between the objects the two tables represent.
A database used by a school application can be taken as an example. Two of the tables it contains are "Student" and "Subject." In real life, a student will take several subjects simultaneously, while a subject will be studied by several students at a time. This is a many-to-many relationship.
Relation databases have redundancy which may be lost in many-to-many relationship.